While the dissimilation of pentitols by Streptococcus avium and certain strains of Lactobacillus casei is catalyzed by similar enzymatic mechanisms, the manner in which the two groups of bacteria regulate and induce pentitol metabolizing enzymes appears to be different. The pentitol: PEP phosphotransferase system and pentitol dehydrogenases are gratuitously induced when L. casei is grown on gluconate or ribose; this does not occur when S. avium is grown on the same substrates. The transport systems for ribitol and xylitol differ from the sugar and sugar alcohol transport systems studied in enteric bacteria and staphylococci in their requirement for specific soluble factors other than enzyme I and histidine-containing phosphorylating protein. The Cytophaga species isolated from the gingival pockets of patients with periodontitis have been further characterized. Transition from anaerobic to aerobic growth is accompanied by the appearance of a completely functional tricarboxylic acid cycle; a complete alteration of metabolic end products form glucose and a drastic change in final cell yield and culture pH. Adsorption of these gram negative gliding bacteria to hydroxyapatite conforms to the Langmuir isotherm equation indicating that a receptor-specific interaction between bacterium and substrate takes place.